A respiratory valve assembly (1), such as in a manual resuscitator, has a carbon dioxide color change indicator element (52) in a disc shape housing (50) arranged to clip onto a grove (59) on the valve assembly. Expiratory and inspiratory gas is supplied to the housing via two flexible tubes (60) and (61) extending side-by-side from the valve assembly (1) to the indicator housing (50) so that the indicator can be undipped from the valve and repositioned if desired.